Tycho Brahe (December 14, 1546 - October 24, 1601)

Tycho (whose original name was Tyge Brahe) was born in Skane (then Denmark,
now Sweden) on December 14, 1546 and grew up as a nobleman in an uncle's
castle. At age 13, he went to the Lutheran university at Copenhagen and became
known to Johannes Pratensis, a professor of medicine, who stimulated first
interests in astronomy, supported by the experience of a solar eclipse in 1560.
He studied law in various European places, including Leipzig, Rostock, Basle
and Augsburg. On December 29, 1566 he duelled with another Danish nobleman,
Manderup Parsbjerg, over th3e question who was the better mathematician; as
Parsbjerg was apparently at least the better swordsman, Tycho lost a portion
of his nose, and from then on, was wearing a metal nose prothesis longly
thought to be made of gold or silver (but lately shown to consist partly of
copper in June, 1901 when Tycho's body was exhumed). In 1570, he settled in
Denmark.

On November 11, 1572, on his way home, Tycho was surprised by a "new" star in
Cassiopeia which was shining at about the brightness of Jupiter and which had
not been seen in this place before. He had found the famous
Supernova of 1572 which he observed for 16 months until March, 1574, and
described it in his book, "Stella Nova."

Consequently, Tycho turned to professional astronomy and with the help of
Danish King Frederick II, established his observatories "Uranienburg" (1580)
and "Sternenburg" (or Stjerneborg, 1584) on the island Hven, where he performed
astrometric measures which were the best in pre-telescopic times. Results were
the discovery that comets are situated in space beyond the Moon, of Lunar
variation and acurate planetary pathes in the sky. Of praticular importance
were his considerably acurate planetary observations, notably of Mars; these
data were used by Kepler to deduce the laws of planetary motion
(Kepler's laws).

Tycho also invented a new (the "Tychonic") world system, opposing Copernicus
because of the lack of observable stellar parallaxes: In his system, the
planets Mercury, Venus, Mars, Jupiter and Saturn should orbit the Sun, but the
Sun together with the Moon should revolve around an Earth at rest.
Moreover, he was engaged in astrology and alchimy.

Tycho left Denmark after the death of King Frederick in 1597, and in 1600, went
to Prague to accept a post as Emperial Mathematician and Astronomer at the
court of Rudolf II.
He died on October 24, 1601 at Benatky near Prague.

Tycho's observing place, Stjerneborg on the island Hven, now Swedish territory,
has been reconstructed and can be visited as the Tycho Brahe Museum, see e.g.
the description in De Vorkin (2003).

His great star catalogue, of epoch 1601, was published after his death only, by
Johannes Kepler in 1602-1603, and contained 777 stars. A later edition was
enlartged to 1005 stars. Of these, Tycho described six as nebulous, of which
only one, the Praesepe Cluster (M44),
corresponds to a real object, while the others are merely asterisms, or stars
erroneously seen as nebulous due to unknown reasons.

It is surprising that this great observer failed to detect the two most
prominent nebulae, the Orion Nebula (M42) and the Andromeda "Nebula" (M31).
For the latter, this resulted in speculations about a possible variability
in brightness, e.g. by Bullialdus (1667) and
Le Gentil (1759).